A well bore may be drilled in the earth for various purposes, such as hydrocarbon extraction, geothermal energy, or water. After a well bore is drilled, the well bore is typically lined with casing. The casing preserves the shape of the well bore as well as provides a sealed conduit for fluid to be transported to the surface.
In general, it is desirable to maintain a clean well bore to prevent possible complications that may occur from debris in the well bore. For example, accumulation of debris can prevent free movement of tools through the well bore during operations, as well as possibly interfere with production of hydrocarbons or damage tools. Potential debris includes cuttings produced from the drilling of the well bore, metallic debris from the various tools and components used in operations, and corrosion of the casing. Smaller debris may be circulated out of the well bore using drilling fluid; however, larger debris is sometimes unable to be circulated out of the well. Also, the well bore geometry may affect the accumulation of debris. In particular, horizontal or otherwise significantly angled portions in a well bore can cause the well bore to be more prone to debris accumulation. Because of this recognized problem, many tools and methods are currently used for cleaning out well bores.
One type of tool known in the art for collecting debris is the junk catcher, sometimes referred to as a junk basket, junk boot, or boot basket, depending on the particular configuration for collecting debris and the particular debris to be collected. The different junk catchers known in the art rely on various mechanisms to capture debris from the well bore. A common link between most junk catchers is that they rely on the movement of fluid in the well bore to capture the sort of debris discussed above. The movement of the fluid may be accomplished by surface pumps or by movement of the string of pipe or tubing to which the junk catcher is connected. Hereinafter, the term “work string” will be used to collectively refer to the string of pipe or tubing and all tools that may be used along with the junk catchers discussed herein. For describing fluid flow, “uphole” refers to a direction in the well bore that is towards the surface, while “downhole” refers to a direction in the well bore that is towards the distal end of the well bore.
A junk catcher is disclosed in U.S. Pat. No. 4,111,262 issued to Duncan, which is incorporated herein by reference in its entirety. An embodiment disclosed by Duncan is shown in FIG. 1. The particular configuration shown in FIG. 1 is commonly referred to as a junk boot or boot basket because of the boot 102 that is disposed on the tool body 101. The junk boot shown in FIG. 1 includes an upper connection 108 and a lower connection 109 for connecting to other components in the work string (not shown). The junk boot may be deployed along any portion of the work string, but is generally near the downhole end (i.e. deepest in the well bore) in order to collect debris that cannot be circulated out of the well. The junk boot shown in FIG. 1 functions through the use of fluid (not shown) pumped through the work string that goes through the internal cylindrical wall 113 and exits through tools located below the junk boot. The fluid, along with any suspended debris, travels uphole towards the surface in the annular space between the boot 102 and the casing wall 120. At the location of the boot 102, flow is restricted because of the large outer diameter of the boot 102. The restricted area creates faster flow. As the fluid passes the boot 102, it suddenly decelerates because of the larger annular space between the outer diameter of the tool body 101 and the casing wall 120. This causes some of the debris 105 (especially larger and denser debris) to settle out of the fluid and enter into the opening 106 at the top of the boot 102. The junk boot continues to function in this manner until the boot 102 is filled with the debris 105.
Another type of junk catcher is disclosed in U.S. Pat. No. 4,059,155 issued to Greer, which is incorporated herein by reference in its entirety. An embodiment disclosed by Greer is shown in FIGS. 2A and 2B. The particular configuration shown in FIGS. 2A and 2B is typically referred to as a reverse-circulating junk basket. The junk basket shown in FIG. 2 includes an upper body 206, a debris chamber 201, and a lower body 209. The upper body 206 has a connection 208 for connecting to a work string (not shown). At the end of the lower body 209, the junk basket includes a mill shoe 210, which can be used with rotation to break up debris or provide a core sample to be trapped in the debris chamber 201. Without explaining any additional valves and mechanisms used for reverse-circulation, the concept works by jetting fluid (not shown) through downward holes 212, which cause the fluid to exit the junk basket and flow downhole between the outside diameter of the junk basket and the well bore wall or casing if present (not shown). When the fluid reaches the downhole end of the junk basket, the fluid turns uphole and enters the lower body 209. This is referred to as “reverse-circulation” because fluid typically flows downhole through the center of a tool and uphole outside of the tool.
When the fluid turns uphole, it carries debris 105 into the debris chamber 201. Two sets of fingers 205 are disposed below the debris chamber 201 in the lower body 209. The fingers 205 are biased towards a closed position as shown in FIG. 2B. Hinges 215 allow the fingers 205 to pivot upward into an open position with fluid flow to allow debris 105 to pass. The fluid continues to flow uphole to the upper body 206 as the debris 105 is filtered out in the debris chamber 201. The fluid is jetted out of the upper body through upward holes 211 (shown as dashed lines) and into the well bore. When fluid flow ceases or is sufficiently reduced, the fingers 205 return to a closed position, trapping the debris 105 within the debris chamber 201. The size of the debris 105 collected within the debris chamber 201 is determined by the spacing between the fingers 205. Smaller gaps between the fingers 205 allow for the collecting of smaller debris. Similar reverse-circulating junk catchers may use flapper valves in place of fingers 205 in order to catch small debris such as sand and gravel. Some reverse-circulating junk catchers may use extended debris chambers made of tubing in order to collect greater amounts of debris. The debris 105 being collected, the pumping equipment being used, and various well parameters affect the total length of the debris chamber, and, as a result, the total amount of debris that may be collected.
Junk boots, such as the one shown in FIG. 1, are limited in the outer diameter of the junk boot 102 because fluid (and debris 105 suspended therein) must still be able to flow around the junk boot 102. This limits the amount of debris that can be collected within the junk boot 102 per foot of axial length. To collect additional debris 105, the junk boot 102 must be lengthened, or additional junk catchers may be used in the work string. A known issue with reverse-circulating junk catchers, such as the one shown in FIGS. 2A and 2B, is that they must be positioned near the end of the work string in order to be effective in collecting debris. Further, only one reverse-circulating junk catcher may be used in a work string.